If this operating element is encoded in an analog manner, an operating instance of the operating element would be able to be detected by a comparator or with the help of an analog-digital converter and a series-connected microcontroller. In the latter case, the microcontroller would either need to be permanently switched on for the voltage evaluation or regularly activated. This is associated with significant additional expenditure. However, if an operation is detected in connection with a comparator, the problem arises that voltage fluctuations, structural component tolerances, climatic influences, or also ageing or contamination cause the input level to shift so significantly that clear detection of a signal change is not able to be ensured over the entire lifetime. In particular, contamination of the operating element that is expressed, for example, in a parasitic resistor in parallel with the actual circuit element leads to problems regarding reliable operation detection. Therefore, an object of the present invention is to reliably detect operation of an analog encoded operating element in order to activate a control unit.